[Boatanchors] Bendix RA-1 BFO Problem

[Roger Basford]

Hi All,

I have a Bendix RA-1B aircraft receiver with a BFO fault and I was wondering 
if anyone out there with another RA-1 could do some voltage checks for me? 
The manual states that the CW oscillator V8 (6K7G) runs at "very low 
operating voltage". V8 plate and screen are strapped together and fed from 
the B+ rail via a resistor chain. Switching on the BFO is done by grounding 
the cathode of V8 through the coil assembly.

At the tube plate I read 22 Volts with the BFO off. With BFO on this voltage 
drops to 5 Volts at about 0.5ma - far too low, I'm sure, to operate. There 
doesn't appear to be any problem with the associated resistors or decoupling 
caps, or with the contents of the BFO coil can. Disconnecting the BFO output 
to IF transformer FL2 has no effect. A new 6K7G hasn't helped. The PSU is 
homebrew using a 14 to 240 V DC dynamotor with the receiver internally 
strapped for 12 V operation as per the manual. All other receiver functions 
are OK.

Any assistance/advice gratefully received!

73,

Roger Basford - G3VKM, Norfolk, England. 



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